Tunable resonators using high dielectric constant ferrite rods

ABSTRACT

Disclosed are single-piece magnetically tunable ferrite rods that can be used for radio-frequency (RF) applications, and methods of manufacturing the resonators using synthetic garnets. In some embodiments, a separate tuner need not be used in the resonator during magnetic tuning. Examples of fabrication methods and RF-related properties are also disclosed.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This Application claims from the benefit of U.S. Provisional Application No. 61/917,843, filed Dec. 18, 2013, titled “TUNABLE RESONATORS USING HIGH DIELECTRIC CONSTANT FERRITE RODS,” the entirety of which is incorporated herein by reference.

RELATED APPLICATIONS

This application is related to Applicant's co-pending application entitled EFFECTIVE SUBSTITUTIONS FOR RARE EARTH METALS IN COMPOSITIONS AND MATERIALS FOR ELECTRONIC APPLICATIONS, Ser. No. 13/183,329, filed on Jul. 14, 2011 and issued as U.S. Pat. No. 8,696,925 on Apr. 15, 2014, and Applicant's co-pending application entitled RARE EARTH REDUCED GARNET SYSTEMS AND RELATED MICROWAVE APPLICATIONS, Ser. No. 13/484,018, filed on May 30, 2012 and published as US 2013/0050041 A1 on Feb. 28, 2013, the entirety of each which is hereby incorporated by reference.

BACKGROUND

1. Field

Embodiments of the disclosure relate to methods of preparing compositions and materials useful in electronic applications, and in particular, useful as a single-piece tunable resonator.

2. Description of the Related Art

Various crystalline materials with magnetic properties have been used as components in electronic devices such as cellular phones, biomedical devices, and RFID sensors. Garnets are crystalline materials with ferrimagnetic properties particularly useful in RF electronics operating in the lower frequency portions of the microwave region. Many microwave magnetic materials are derivatives of Yttrium Iron Garnet (YIG), a synthetic form of garnet widely used in various telecommunication devices largely because of its favorable magnetic properties such as narrow line absorption at its ferromagnetic resonance frequency. YIG is generally composed of Yttrium, Iron, Oxygen, and possibly doped with one or more other rare earth metals such as the Lanthanides or Scandium. However, the supply of rare earth elements such as Yttrium has recently become increasingly restricted, thus resulting in correspondingly steep increases in cost. As such, there is a need to find a cost-effective substitute for rare earth elements in synthetic garnet structures that does not compromise the magnetic properties of the material and can be used for microwave applications.

Filters often need to be remotely reconfigured to different frequencies. This is currently done in cellular infrastructure base stations either off-site by removal and mechanical re-tuning, or on-site by electric motor-driven tuners activated remotely. An alternative method is the use of magnetically tuned resonators which are faster (micro-second tuning) than motor driven tuners (milli-second tuning).

Previous magnetically tuned solutions have used single crystal based YIG resonators either with YIG spheres or epitaxially deposited YIG on a lattice matched substrate. These solutions are large and expensive. Another approach is the use of composite resonators of dielectric and magnetic elements which are also large and expensive.

SUMMARY

Disclosed herein is a tunable resonator system which can comprise a cavity, a single-piece high-dielectric resonator comprising a tunable magnetic element formed out of one material and located within the cavity, and an adjustable magnetic field.

In some embodiments, the resonator can have millisecond tuning. In some embodiments, the resonator can have micro-second tuning. In some embodiments, the cavity can have a silver coating. In some embodiments, the single-piece high-dielectric resonator can have a dielectric constant of 26.7. In some embodiments, the resonator can be a TE mode resonator. In some embodiments, the resonator can be a TM mode resonator.

In some embodiments, the material can be a synthetic garnet. In some embodiments, the synthetic garnet can be Bi_(x)Ca_(y+2x)Y_(3−x−y−2z)Fe_(5−y−z)Zr_(y)V_(z)O₁₂. In some embodiments, the synthetic garnet can be Bi_(x)Y_(3−x−0.35)Ca_(0.35)Zr_(0.35)Fe_(4.65)O₁₂. In some embodiments, the synthetic garnet can be Bi(Y,Ca)₂Fe_(4.2)M^(I) _(0.4)M^(II) _(0.4)O₁₂. In some embodiments, the synthetic garnet can be Y_(2.15−2x)Bi_(0.5)Ca_(0.35+2x)Zr_(0.35)V_(x)Fe_(4.65−x)O₁₂. In some embodiments, the synthetic garnet can be Bi_(0.9)Ca_(0.9x)Y_(2.1−0.9x)(Zr_(0.7)Nb_(0.1))_(x)Fe_(5−0.8x)O₁₂. In some embodiments, the synthetic garnet can be Bi_(0.9)Ca_(0.9+2x)Y_(2.1−0.9−2x)Zr_(0.7)Nb_(0.1)V_(x)Fe_(4.2−x)O₁₂. In some embodiments, the synthetic garnet can be Bi_(1.4)Ca_(0.55+2x)Y_(1.05−2x)Zr_(0.55)V_(x)Fe_(4.45−x)O₁₂. In some embodiments, the synthetic garnet can be Y₂CaFe_(4.4)Zr_(0.4)Mo_(0.2)O₁₂. In some embodiments, the synthetic garnet can be a material selected from the group consisting of BiY₂Fe_(4.6)In_(0.4)O₁₂, BiCa_(0.4)Y_(1.6)Fe_(4.6)Zr_(0.4)O₁₂, BiCa_(0.4)Y_(1.6)Fe_(4.6)Ti_(0.4)O₁₂, BiCa_(0.8)Y_(1.2)Fe_(4.6)Sb_(0.4)O₁₂, BiY₂Fe_(4.6)Ga_(0.4)O₁₂, BiCa_(1.2)Y_(0.8)Fe_(4.2)In_(0.4)Mo_(0.4)O₁₂, BiY_(1.2)Ca_(0.8)Fe_(4.2)Zn_(0.4)Mo_(0.4)O₁₂, BiY_(1.2)Ca_(0.8)Fe_(4.2)Mg_(0.4)Mo_(0.4)O₁₂, BiY_(0.4)Ca_(1.6)Fe_(4.2)Zr_(0.4)Mo_(0.4)O₁₂, BiY_(0.4)Ca_(1.6)Fe_(4.2)Sn_(0.4)Mo_(0.4)O₁₂, BiCa₂Fe_(4.2)Ta_(0.4)Mo_(0.4)O₁₂, BiCa₂Fe_(4.2)Nb_(0.4)Mo_(0.4)O₁₂, BiY_(0.8)Ca_(1.2)Fe_(4.6)Mo_(0.4)O₁₂, and BiY_(0.4)Ca_(1.6)Fe_(4.2)Ti_(0.4)Mo_(0.4)O₁₂.

Further disclosed herein is a filtration system which can comprise an antenna, a subsystem, a converter, and at least one filter having a single-piece high-dielectric resonator comprising a tunable magnetic element formed out of one material.

Also disclosed herein is method of forming a tunable resonator system which can comprise preparing a powder for a high-dielectric material, forming the powder into a shape, and sintering the formed powder into a single-piece high-dielectric resonator comprising a tunable magnetic element formed out of one material and located within the cavity.

In some embodiments, the method can further comprise inserting the single-piece high-dielectric resonator into a cavity and applying an adjustable magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows how materials having one or more features described herein can be designed, fabricated, and used.

FIG. 2 depicts a Yttrium based garnet crystal lattice structure;

FIG. 3 is an example graph depicting variations of material properties versus varying levels of Vanadium in crystalline compositions represented by the formula Y_(2.15−2x)Bi_(0.5)Ca_(0.35+2x)Zr_(0.35)V_(x)Fe_(4.65−x)O₁₂, where x=0.1 to 0.8.

FIG. 4 is an example graph depicting variations of material properties versus varying levels of (Zr, Nb) in crystalline compositions represented by the formula Bi_(0.9)Ca_(0.9x)Y_(2.1−0.9x)(Zr_(0.7)Nb_(0.1))_(x)Fe_(5−0.8x)O₁₂, where x=0.5 to 1.0.

FIGS. 5A-5G are example graphs depicting the relationship between firing temperature and various properties at varying levels of Vanadium in crystalline compositions represented by the formula Bi_(0.9)Ca_(0.9+2x)Zr_(0.7)Nb_(0.1)V_(x)Fe_(4.2−x)O₁₂ where x=0-0.6.

FIG. 6 is an example graph depicting best linewidth versus composition of varying Vanadium content in crystalline compositions represented by the formula Bi_(0.9)Ca_(0.9+2x)Zr_(0.7)Nb_(0.1)V_(x)Fe_(4.2−x)O₁₂ where x=0-0.6.

FIG. 7 is an example graph illustrating the properties of crystal compositions represented by the formula Bi_(1.4)Ca_(1.05−2x)Zr_(0.55)V_(x)Fe_(4.45−x)O₁₂, where x=0-0.525.

FIG. 8 illustrates an example process flow for making a modified synthetic garnet having one or more features described herein.

FIG. 9 shows an example ferrite device having one or more garnet features as described herein.

FIG. 10 shows various properties as functions of Zr content for an example composition Bi_(0.5)Y_(2.5−x)Ca_(x)Zr_(x)Fe_(5−x)O₁₂ where Bi⁺³ content is substantially fixed at approximately 0.5 while Zr⁺⁴ content is varied from 0 to 0.35.

FIG. 11 shows various properties as functions of Bi content for an example composition Bi_(x)Y_(2.65−x)Ca_(0.35)Zr_(0.35)Fe_(4.65)O₁₂ where Zr⁺⁴ content is substantially fixed at approximately 0.35 while Bi⁺³ content is varied.

FIG. 12 shows dielectric constant and density as functions of Bi content for the example composition of FIG. 11.

FIG. 13 shows plots of various properties as functions of Zr content that extends beyond the 0.35 limit of the example composition of FIG. 10.

FIG. 14 shows plots of various properties as functions of V⁺⁵ content when Bi content is approximately 1.4 and Zr content is approximately 0.55 for the example composition of FIG. 13.

FIGS. 15A and 15B show examples of size reduction that can be implemented for ferrite devices having one or more features as described herein.

FIGS. 16A and 16B show an example circulator/isolator having ferrite devices as described herein.

FIG. 17 shows insertion loss plots and return loss plots for two example 25 mm circulators, where one is based on a YCaZrVFe garnet system with dielectric constant of 14.4, and another is based on a Yttrium free BiCaZrVFe garnet system with dielectric constant of 26.73.

FIGS. 18A and 18B show s-parameter data for an example 10 mm circulator device having the high-dielectric Yttrium free BiCaZrVFe garnet system of FIG. 17.

FIG. 19 shows an example of a packaged circulator module.

FIG. 20 shows an example RF system where one or more of circulator/isolator devices as described herein can be implemented.

FIG. 21 shows side and top viewpoints of embodiments of a cavity containing a resonator.

FIG. 22 shows an embodiment of a two-piece rod.

FIG. 23 shows an embodiment of a one-piece tunable rod.

FIGS. 24A and 24B show embodiments of a rectangular and cylindrical one-piece tunable rod.

FIG. 25 shows a side view of an embodiment of a one-piece tunable rod.

FIG. 26 shows a graph of frequency and Q as compared to the Z-axis H field for embodiments of a one-piece tunable rod.

FIG. 27 shows an embodiment of a cavity containing a one-piece tunable rod.

FIG. 28 shows a graph of frequency and Q as compared to a Z-axis H field for embodiments of a one-piece tunable rod.

FIG. 29 shows a process that can be implemented to form an embodiment of a cavity having a tunable one-piece tunable rod.

FIG. 30 shows a process that can be implemented to magnetically tune an embodiment of a one-piece tunable rod.

FIG. 31 shows an example RF system where an embodiment of a one-piece tunable rod can be used.

FIG. 32 shows a process that can be implemented to fabricate a ceramic material having one or more features as described herein.

FIG. 33 shows a process that can be implemented to form a shaped object from powder material described herein.

FIG. 34 shows examples of various stages of the process of FIG. 33.

FIG. 35 shows a process that can be implemented to sinter formed objects such as those formed in the example of FIGS. 33 and 34.

FIG. 36 shows examples of various stages of the process of FIG. 35.

DETAILED DESCRIPTION

Disclosed herein are embodiments of tunable resonators, specifically tunable resonator rods without separate tuning elements, as well as the materials for forming the resonators and methods of making the materials/resonators. Therefore, the resonator rods can be formed of a single piece of material, which is advantageous over multiple-piece resonator rods currently in use.

The headings provided herein, if any, are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.

Synthetic Garnets

FIG. 1 schematically shows how one or more chemical elements (block 1), chemical compounds (block 2), chemical substances (block 3) and/or chemical mixtures (block 4) can be processed to yield one or more materials (block 5) having one or more features described herein. In some embodiments, such materials can be formed into ceramic materials (block 6) configured to include a desirable dielectric property (block 7), a magnetic property (block 8) and/or an advanced material property.

In some embodiments, a material having one or more of the foregoing properties can be implemented in applications (block 10) such as radio-frequency (RF) application. Such applications can include implementations of one or more features as described herein in devices 12. In some applications, such devices can further be implemented in products 11. Examples of such devices and/or products are described herein.

Disclosed herein are methods of modifying synthetic garnet compositions, such as Yttrium Iron Garnet (YIG), to reduce or eliminate the use of rare earth metals in such compositions. Also disclosed herein are synthetic garnet materials having reduced or no rare earth metal content, methods of producing the materials, and the devices and systems incorporating such materials. The synthetic garnet materials prepared according to embodiments described in the disclosure exhibit favorable magnetic properties for microwave magnetic applications. These favorable properties include but are not limited to low magnetic resonance line width, optimized density, saturation magnetization and dielectric loss tangent. Applicants have surprisingly found that when garnet compositions are doped with certain combinations of ions and prepared using certain processing techniques, a significant amount if not all of the rare earth elements can be substituted and yet still result in microwave magnetic crystalline materials with comparable, if not superior, performance characteristics as commercially available garnets containing Yttrium (Y) or other rare earth elements.

Synthetic garnets typically have the formula unit of A₃B₅O₁₂, where A and B are trivalent metal ions. Yttrium Iron Garnet (YIG) is a synthetic garnet having the formula unit of Y₃Fe₅O₁₂, which includes Yttrium (Y) in the 3+ oxidation state and Iron (Fe) in the 3+ oxidation state. The crystal structure of a YIG formula unit is depicted in FIG. 2. As shown in FIG. 2, YIG has a dodecahederal site, an octahedral site, and a tetrahedral site. The Y ions occupy the dodecahedral site while the Fe ions occupy the octahedral and tetrahedral sites. Each YIG unit cell, which is cubic in crystal classifications, has eight of these formula units.

The modified synthetic garnet compositions, in some embodiments, comprise substituting some or all of the Yttrium (Y) in Yttrium Iron Garnets (YIG) with a combination of other ions such that the resulting material maintains desirable magnetic properties for microwave applications. There have been past attempts toward doping YIG with different ions to modify the material properties. Some of these attempts, such as Bismuth (Bi) doped YIG, are described in “Microwave Materials for Wireless Applications” by D. B. Cruickshank, which is hereby incorporated by reference in its entirety. However, in practice ions used as substitutes may not behave predictably because of, for example, spin canting induced by the magnetic ion itself or by the effect of non-magnetic ions on the environment adjacent magnetic ions, reducing the degree alignment. Thus, the resulting magnetic properties cannot be predicted. Additionally, the amount of substitution is limited in some cases. Beyond a certain limit, the ion will not enter its preferred lattice site and either remains on the outside in a second phase compound or leaks into another site. Additionally, ion size and crystallographic orientation preferences may compete at high substitution levels, or substituting ions are influenced by the ion size and coordination of ions on other sites. As such, the assumption that the net magnetic behavior is the sum of independent sub-lattices or single ion anisotropy may not always apply in predicting magnetic properties.

Considerations in selecting an effective substitution of rare earth metals in YIG for microwave magnetic applications include the optimization of the density, the magnetic resonance linewidth, the saturation magnetization, the Curie temperature, and the dielectric loss tangent in the resulting modified crystal structure. Magnetic resonance is derived from spinning electrons, which when excited by an appropriate radio frequency (RF) will show resonance proportional to an applied magnetic field and the frequency. The width of the resonance peak is usually defined at the half power points and is referred to as the magnetic resonance linewidth. It is generally desirable for the material to have a low linewidth because low linewidth manifests itself as low magnetic loss, which is required for all low insertion loss ferrite devices. The modified garnet compositions according to preferred embodiments of the present invention provide single crystal or polycrystalline materials with reduced Yttrium content and yet maintaining low linewidth and other desirable properties for microwave magnetic applications.

In some embodiments, a Yttrium based garnet is modified by substituting Bismuth (Be⁺) for some of the Yttrium (Y³⁺) on the dodecahedral sites of the garnet structure in combination with introducing one or more ions, such as divalent (+2), trivalent (+3), tetravalent (+4), pentavalent (+5) or hexavalent (+6) non-magnetic ions to the octahedral sites of the structure to replace at least some of the Iron (Fe³⁺). In a preferred implementation, one or more high valency non-magnetic ions such as Zirconium (Zr⁴⁺) or Niobium (Nb⁵⁺) can be introduced to the octahedral sites.

In some embodiments, a Yttrium based garnet is modified by introducing one or more high valency ions with an oxidation state greater than 3+ to the octahedral or tetrahedral sites of the garnet structure in combination with substituting Calcium (Ca²⁺) for Yttrium (Y³⁺) in the dodecahedral site of the structure for charge compensation induced by the high valency ions, hence reducing the Y³⁺ content. When non-trivalent ions are introduced, valency balance is maintained by introducing, for example, divalent Calcium (Ca²⁺) to balance the non-trivalent ions. For example, for each 4+ ion introduced to the octahedral or tetrahedral sites, one Y³⁺ ion is substituted with a Ca²⁺ ion. For each 5+ ion, two Y³⁺ ions are replaced by Ca²⁺ ions. For each 6+ ion, three Y³⁺ ions are replaced by Ca²⁺ ions. For each 6+ ion, three Y³⁺ ions are replaced by Ca²⁺ ions. In one implementation, one or more high valence ions selected from the group consisting of Zr⁴⁺, Sn⁴⁺, Ti⁴⁺, Nb⁵⁺, Ta⁵⁺, Sb⁵⁺, W⁶⁺, and Mo⁶⁺ is introduced to the octahedral or tetrahedral sites, and divalent Calcium (Ca²⁺) is used to balance the charges, which in turn reduces Y³⁺ content.

In some embodiments, a Yttrium based garnet is modified by introducing one or more high valency ions, such as Vanadium (V⁵⁺), to the tetrahedral site of the garnet structure to substitute for Fe³⁺ to further reduce the magnetic resonance linewidth of the resulting material. Without being bound by any theory, it is believed that the mechanism of ion substitution causes reduced magnetization of the tetrahedral site of the lattice, which results in higher net magnetization of the garnet, and by changing the magnetocrystalline environment of the ferric ions also reduces anisotropy and hence the ferromagnetic linewidth of the material.

In some embodiments, Applicant has found that a combination of high Bismuth (Bi) doping combined with Vanadium (V) and Zirconium (Zr) induced Calcium (Ca) valency compensation could effectively displace all or most of the Yttrium (Y) in microwave device garnets. Applicants also have found that certain other high valency ions could also be used on the tetrahedral of octahedral sites and that a fairly high level of octahedral substitution in the garnet structure is preferred in order to obtain magnetic resonance linewidth in the 5 to 20 Oersted range. Moreover, Yttrium displacement is preferably accomplished by adding Calcium in addition to Bismuth to the dodecahedral site. Doping the octahedral or tetrahedral sites with higher valency ions, preferably greater than 3+, would allow more Calcium to be introduced to the dodecahedral site to compensate for the charges, which in turn would result in further reduction of Yttrium content.

Modified Synthetic Garnet Compositions:

In one implementation, the modified synthetic garnet composition may be represented by general Formula I: Bi_(x)Ca_(y+2x)Y_(3−x−y−2z)Fe_(5−y−z)Zr_(y)V_(z)O₁₂, where x=0 to 3, y=0 to 1, and z=0 to 1.5, more preferably x=0.5 to 1.4, y=0.3 to 0.55, and z=0 to 0.6. In a preferred implementation, 0.5 to 1.4 formula units of Bismuth (Bi) is substituted for some of the Yttrium (Y) on the dodecahedral site, 0.3 to 0.55 formula units of Zirconium (Zr) is substituted for some of the Iron (Fe) on the octahedral site. In some embodiments, up to 0.6 formula units of Vanadium (V) is substituted for some of the Iron (Fe) on the tetrahedral site. Charge balance is achieved by Calcium (Ca) substituting for some or all of the remaining Yttrium (Y). In some other embodiments, small amounts of Niobium (Nb) may be placed on the octahedral site and small amounts of Molybdenum (Mo) may be placed on the tetrahedral site.

In another implementation, the modified synthetic garnet composition may be represented by general Formula II: Bi_(x)Y_(3−x−0.35)Ca_(0.35)Zr_(0.35)Fe_(4.65)O₁₂, where x=0.5 to 1.0, preferably x=0.6 to 0.8, more preferably x=0.5. In this implementation, 0.5 to 1.0 formula units of Bismuth (Bi) is substituted for some of the Yttrium (Y) on the dodecahedral site and Zirconium (Zr) is substituted for some of the Iron (Fe) on the octahedral site. Calcium (Ca²⁺) is added to the dodecahedral site to replace some of the remaining Y to balance the Zr charges. Bi content can be varied to achieve varying material properties while Zr is held fixed at Zr=0.35.

In another implementation, the modified garnet composition may be represented by general Formula III: Bi(Y,Ca)₂Fe_(4.2)M^(I) _(0.4)M^(II) _(0.4)O₁₂, where M^(I) is the octahedral substitution for Fe and can be selected from one or more of the following elements: In, Zn, Mg, Zr, Sn, Ta, Nb, Fe, Ti, and Sb, where M^(II) is the tetrahedral substitution for Fe and can be selected from one or more of the following elements: Ga, W, Mo, Ge, V, Si.

In another implementation, the modified synthetic garnet composition may be represented by general Formula IV: Y_(2.15−2x)Bi_(0.5)Ca_(0.35+2x)Zr_(0.35)V_(x)Fe_(4.65−x)O₁₂, wherein x=0.1 to 0.8. In this implementation, 0.1 to 0.8 formula units of Vanadium (V) is added to the tetrahedral site to substitute for some of the Iron (Fe), and Calcium (Ca) is added to balance the V charges and replace some of the remaining Y while the levels of Bi and Zr remain fixed similar to Formula III. FIG. 3 illustrates variations of material properties in connection with varying levels of V. As shown in FIG. 3, the dielectric constant and density of the material remain largely constant with varying levels of V. Increasing levels of V reduces the 4PiMs by about 160 Gauss for each 0.1 of V. As further shown in FIG. 3, there are no appreciable changes in 3 dB linewidth up to V=0.5.

In another implementation, the modified synthetic garnet composition may be represented by Formula V: Bi_(0.9)Ca_(0.9x)Y_(2.1−0.9x)(Zr_(0.7)Nb_(0.1))_(x)Fe_(5−0.8x)O₁₂, wherein x=0.5 to 1.0. In this implementation, the octahedral substitution is made with two high valency ions: Zr⁴⁺ and Nb⁵⁺ with Bi held constant at 0.9. FIG. 4 illustrates variations of material properties in connection with varying levels of (Zr, Nb). As shown in FIG. 4, the magnetic resonance linewidth decreased with higher octahedral substitutions. The magnetization also fell as the increase in total non-magnetic ions overcomes the higher non-magnetic octahedral substitutions.

In another implementation, the modified synthetic garnet composition may be represented by Formula VI: Bi_(0.9)Ca_(0.9−2x)Y_(2.1−0.9−2x)Zr_(0.7)Nb_(0.1)V_(x)Fe_(4.2−x)O₁₂, wherein V=0-0.6. In this implementation, Vanadium is introduced to the octahedral site in addition to Zr and Nb. When V=0.6, Y is completely replaced. FIGS. 5A-5G illustrate the relationship between firing temperatures and various material properties as V level increases from 0 to 0.6. As illustrated, the 3 dB linewidth, measured in accordance with ASTM A883/A883M-01, tends to remain below 50 Oe at all V levels at firing temperatures below 1040° C. FIG. 6 illustrates the best linewidth at varying firing temperatures versus composition at varying levels of V of one preferred embodiment. In some implementations, the linewidth can be further reduced by annealing the material. The effect of annealing on linewidth of Bi_(0.9)Ca Zr_(0.7)Nb_(0.1)V_(x)Fe_(4.2−x)O₁₂, where x=0.1 to 0.5 is illustrated in Table 1 below.

TABLE 1 Linewidth (Oe) and Curie Temp. (° C.) Data for Bi_(0.90)Ca_(0.9 + 2x)Y_(2.1 − 0.9 − 2x)(Zr, Nb)_(0.8)V_(X)Fe _(4.2 − X)O₁₂ Heat Treatment Heat Heat (Calcined Treatment 3 dB 3 dB Treatment 3 dB Blend + 3 dB 3 dB after (Initial before after (Calcined before 3 dB after Extended before extended Curie Formula Blend) anneal anneal Blend) anneal anneal Milling) anneal anneal Temp V = 0.5 1050 39 25 1030 38 20 1030 38 17 108 V = 0.4 1050 44 27 1030 48 18 1030 42 16 112 V = 0.3 1050 52 32 1030 46 19 1030 48 15 111 V = 0.2 1050 59 43 1030 55 21 1030 62 17 108 V = 0.1 1050 78 62 1030 61 24 1030 55 21 107

In another implementation, the modified synthetic garnet composition may be represented by Formula VI: Bi_(1.4)Ca_(0.55+2x)Y_(1.05−2x)Zr_(0.55)V_(x)Fe_(4.45−x)O₁₂, where x=0-0.525. In this implementation, the level of Bi doping is increased while the level of octahedral substitution is decreased. The material formed has higher Curie temperature and low linewidth. The Vanadium (V) content is varied from 0 to 0.525. When V=0.525, the composition is free of Yttrium. The resulting material achieved a linewidth of 20 Oe without subsequently heat treatment. FIG. 7 illustrates the properties of the material with varying amount of V. As shown in FIG. 7, V drops the dielectric constant rapidly, about 1 unit for each 0.1 of V in the formula unit, and drops the magnetization by about 80 Gauss for each 0.1 of V. Optimizing the processing parameters such as firing conditions have produced linewidth as low as 11 or V at or close to 0.525, which is free of Y. These values are comparable to commercially available Calcium Yttrium Zirconium Vanadium garnets of the same magnetization.

In another implementation, the modified synthetic garnet composition may be represented by Formula VII: Y₂CaFe_(4.4)Zr_(0.4)Mo_(0.2)O₁₂. In this implementation, high valency ion Molybdenum (Mo) is added to the tetrahedral site to create a single phase crystal. In other implementations, the modified synthetic garnet compositions can be represented by a formula selected from the group consisting of: BiY₂Fe_(4.6)In_(0.4)O₁₂, BiCa_(0.4)Y_(1.6)Fe_(4.6)Zr_(0.4)O₁₂, BiCa_(0.4)Y_(1.6)Fe_(4.6)Ti_(0.4)O₁₂, BiCa_(0.8)Y_(1.2)Fe_(4.6)Sb_(0.4)O₁₂, BiY₂Fe_(4.6)Ga_(0.4)O₁₂, BiCa_(1.2)Y_(0.8)Fe_(4.2)In_(0.4)Mo_(0.4)O₁₂, BiY_(1.2)Ca_(0.8)Fe_(4.2)Zn_(0.4)Mo_(0.4)O₁₂, BiY_(1.2)Ca_(0.8)Fe_(4.2) ^(Mg) _(0.4)Mo_(0.4)O₁₂, BiY_(0.4)Ca_(1.6)Fe_(4.2)Zr_(0.4)Mo_(0.4)O₁₂, BiY_(0.4)Ca_(1.6)Fe_(4.2)Sn_(0.4)Mo_(0.4)O₁₂, BiCa₂Fe_(4.2)Ta_(0.4)Mo_(0.4)O₁₂, BiCa₂Fe_(4.2)Nb_(0.4)Mo_(0.4)O₁₂, BiY_(0.8)Ca_(1.2)Fe_(4.6)Mo_(0.4)O₁₂, and BiY_(0.4)Ca_(1.6)Fe_(4.2)Ti_(0.4)Mo_(0.4)O₁₂.

Preparation of the Modified Synthetic Garnet Compositions:

The preparation of the modified synthetic garnet materials can be accomplished by using known ceramic techniques. A particular example of the process flow is illustrated in FIG. 8.

As shown in FIG. 8, the process begins with step 106 for weighing the raw material. The raw material may include oxides and carbonates such as Iron Oxide (Fe₂O₃), Bismuth Oxide (Bi₂O₃), Yttrium Oxide (Y₂O₃), Calcium Carbonate (CaCO₃), Zirconium Oxide (ZrO₂), Vanadium Pentoxide (V₂O₅), Yttrium Vanadate (YVO₄), Bismuth Niobate (BiNbO₄), Silica (SiO₂), Niobium Pentoxide (Nb₂O₅), Antimony Oxide (Sb₂O₃), Molybdenum Oxide (MoO₃), Indium Oxide (In₂O₃), or combinations thereof. In one embodiment, raw material consisting essentially of about 35-40 wt % Bismuth Oxide, more preferably about 38.61 wt %; about 10-12 wt % Calcium Oxide, more preferably about 10.62 wt %; about 35-40 wt % Iron Oxide, more preferably about 37 wt %, about 5-10 wt % Zirconium Oxide, more preferably about 8.02 wt %; about 4-6 wt % Vanadium Oxide, more preferably about 5.65 wt %. In addition, organic based materials may be used in a sol gel process for ethoxides and/or acrylates or citrate based techniques may be employed. Other known methods in the art such as co-precipitation of hydroxides may also be employed as a method to obtain the materials. The amount and selection of raw material depend on the specific formulation.

After the raw material is weighed, they are blended in Step 108 using methods consistent with the current state of the ceramic art, which can include aqueous blending using a mixing propeller, or aqueous blending using a vibratory mill with steel or zirconia media. In some embodiments, a glycine nitrate or spray pyrolysis technique may be used for blending and simultaneously reacting the raw materials.

The blended oxide is subsequently dried in Step 110, which can be accomplished by pouring the slurry into a pane and drying in an oven, preferably between 100-400° C. or by spray drying, or by other techniques known in the art.

The dried oxide blend is processed through a sieve in Step 112, which homogenizes the powder and breaks up soft agglomerates that may lead to dense particles after calcining.

The material is subsequently processed through a pre-sintering calcining in Step 114. Preferably, the material is loaded into a container such as an alumina or cordierite sagger and heat treated in the range of about 800-1000° C., more preferably about 900-950° C. Preferably, the firing temperature is low as higher firing temperatures have an adverse effect on linewidth.

After calcining, the material is milled in Step 116, preferably in a vibratory mill, an attrition mill, a jet mill or other standard comminution technique to reduce the median particle size into the range of about 0.5 micron to 10 microns. Milling is preferably done in a water based slurry but may also be done in ethyl alcohol or another organic based solvent.

The material is subsequently spray dried in Step 118. During the spray drying process, organic additives such as binders and plasticizers can be added to the slurry using techniques known in the art. The material is spray dried to provide granules amenable to pressing, preferably in the range of about 10 microns to 150 microns in size.

The spray dried granules are subsequently pressed in Step 120, preferably by uniaxial or isostatic pressing to achieve a pressed density to as close to 60% of the x-ray theoretical density as possible. In addition, other known methods such as tape casting, tape calendaring or extrusion may be employed as well to form the unfired body.

The pressed material is subsequently processed through a calcining process in Step 122. Preferably, the pressed material is placed on a setter plate made of material such as alumina which does not readily react with the garnet material. The setter plate is heated in a periodic kiln or a tunnel kiln in air or pressure oxygen in the range of between about 850° C.-100° C. to obtain a dense ceramic compact. Other known treatment techniques such as induction heat may also be used in this step.

The dense ceramic compact is machined in the Step 124 to achieve dimensions suitable or the particular applications.

Radio-frequency (RF) applications that utilize synthetic garnet compositions can include ferrite devices having relatively low magnetic resonance linewidths (e.g., approximately 11 Oe or less) as described in reference to FIGS. 2-8. RF applications can also include devices, methods, and/or systems having or related to garnet compositions having reduced or substantially nil rare earth content. As described herein, such garnet compositions can be configured to yield relatively high dielectric constants; and such a feature can be utilized to provide advantageous functionalities. It will be understood that at least some of the compositions, devices, and methods described in reference to FIGS. 2-8 can be applied to such implementations.

FIG. 9 shows a radio-frequency (RF) device 200 having garnet structure and chemistry, and thus a plurality of dodecahedral structures, octahedral structures, and tetrahedral structures. The device 200 can include garnet structures (e.g., a garnet structure 220) formed from such dodecahedral, octahedral, and tetrahedral structures. Disclosed herein are various examples of how dodecahedral sites 212, octahedral sites 208, and tetrahedral sites 204 can be filled by or substituted with different ions to yield one or more desirable properties for the RF device 200. Such properties can include, but are not limited to desirable RF properties and cost-effectiveness of manufacturing of ceramic materials that can be utilized to fabricate the RF device 200. By way of an example, disclosed herein are ceramic materials having relatively high dielectric constants, and having reduced or substantially nil rare earth contents.

Some design considerations for achieving such features are now described. Also described are example devices and related RF performance comparisons. Also described are example applications of such devices, as well as fabrication examples.

Rare Earth Garnets:

Garnet systems in commercial use typically belong to a series of compositions that can be expressed as Y_(3−x)(RE or Ca)_(x)Fe_(2−y)(Me)_(y)Fe_(3−z)(Me′)_(z)O₁₂, where “RE” represents a non-Y rare earth element. The non-Y rare earth element (RE) can be, for example, Gd for temperature compensation of magnetization, with small amounts of Ho sometimes used for high power doping purposes. Rare earths are typically trivalent and occupy dodecahedral sites. “Me” in octahedral sites is typically non-magnetic (e.g., typically Zr⁺⁴, although In⁺³ or Sn⁺⁴ can been used, typically at around y=0.4 in the formula). “Me” in tetrahedral sites is typically non-magnetic (e.g., typically Al⁺³ or V⁺⁵, where z can vary from 0 to around 1 in the formula to give a range of magnetizations). Ca⁺² is typically used in dodecahedral sites for valency compensation when the octahedral or tetrahedral substitution is an ion of valency>3. Based on the foregoing, one can see that such commercial garnet systems contain greater than 40% Y or other RE elements, with the balance mainly Fe⁺³ on octahedral and tetrahedral sites.

Ferrite Device Design Considerations:

Magnetization (4πM_(s)) of ferrite devices for RF applications such as cellular infrastructure typically operate at 400 MHz to 3 GHz in an above-resonance mode. To achieve typical bandwidths of about 5 to 15%, magnetizations in a range of approximately 1,000 to 2,000 Gauss (approximately 0.1 to 0.2 Tesla) are desired.

Magnetic losses associated with ferrite devices can be determined by a ferrimagnetic resonance linewidth ΔH_(o). Values for such linewidth are typically less than about 30 Oersted (about 0.377 Ampere-turns/meter), and are typically equivalent to K₁/M_(s), where K₁ is a first order magnetocrystalline anisotropy, determined by the anisotropy of the Fe⁺³ ion in two of its sites if non-magnetic Y is the only RE. There can also be a fractional porosity (p) contribution to linewidth, approximately 4πM_(s)×p.

Dielectric losses associated with ferrite devices are typically selected so that loss tangent δ satisfies a condition tan δ<0.0004. The Curie temperature associated with ferrite devices can be expected to exceed approximately 160° C. for the above range of magnetizations.

Bismuth Garnets:

Single crystal materials with a formula Bi_((3−2x))Ca_(2x)Fe_(5−x)V_(x)O₁₂ have been grown in the past, where x was 1.25. A 4πM_(s) value of about 600 Gauss was obtained (which is suitable for some tunable filters and resonators in a 1-2 GHz range), with linewidths of about 1 Oersted, indicating low intrinsic magnetic losses for the system. However, the level of Bi substitution was only about 0.5 in the formula.

Attempts to make single phase polycrystalline materials (with a formula Bi_(3−2x)Ca_(2x)V_(x)Fe_(5−x)O₁₂) similar to the single crystal materials were successful only in a region of x>0.96, effectively confining the 4πM_(s) to less than about 700 Oersted and resulting in poor linewidths (greater than 100 Oersted). Small amounts of Al⁺³ reduced the linewidth to about 75 Oersted, but increased Al⁺³ reduced 4πM_(s). Bi substitution was only about 0.4 in the formula for these materials.

For Faraday rotation devices, the Faraday rotation can be essentially proportionate to the level of Bi substitution in garnets, raising interest in increasing the level of substitution. Anisotropy is generally not a major factor for optical applications, so substitution on the octahedral and tetrahedral site can be based on maximizing the rotation. Thus, in such applications, it may be desirable to introduce as much Bi⁺³ into the dodecahedral site as possible. The maximum level of Bi⁺³ can be influenced by the size of the dodecahedral rare earth trivalent ion, and can vary between 1.2 and 1.8 in the formula.

In some situations, the level of Bi⁺³ substitution can be affected by substitutions on the other sites. Because Bi⁺³ is non-magnetic, it can influence the Faraday rotation through its effect on the tetrahedral and octahedral Fe⁺³ ions. Since this is thought to be a spin-orbital interaction, where Bi⁺³ modifies existing Fe⁺³ pair transitions, one can expect both a change in the anisotropy of the Fe⁺³ ions and optical effects including large Faraday rotation. The Curie temperature of Bi⁺³ substituted YIG can also increase at low Bi⁺³ substitution.

Bi Substitution in Polycrystalline Garnets:

To see the effects (e.g., low magnetocrystalline anisotropy and hence low magnetic losses) that can result from combinations of Bi⁺³ on the dodecahedral site and Zr⁺⁴ on the octahedral site, following approaches were tested. The first example configuration included fixed Bi and variable Zr in a formula Bi_(0.5)Y_(2.5−x)Ca_(x)Zr_(x)Fe_(5−x)O₁₂, where x varied from approximately 0 to 0.35. The second example configuration included fixed Zr and variable Bi in a formula Bi_(x)Y_(2.65−x)Ca_(0.35)Zr_(0.35)Fe_(4.65)O₁₂, where x varied from approximately 0.5 to 1.4.

FIG. 10 shows various properties as functions of Zr content for the first configuration (Bi_(0.5)Y_(2.5−x)Ca_(x)Zr_(x)Fe_(5−x)O₁₂) where Bi⁺³ content was fixed at approximately 0.5 while Zr⁺⁴ content was varied from 0 to 0.35. From the plots, one can see that the 0.5 Bi material at zero Zr has a relatively high linewidth (near 80 Oe after porosity correction). This is in contrast to standard Y₃Fe₅O₁₂, which has a much lower corrected value of about 17 Oe, indicating that non-magnetic Bi⁺³ can substantially raise the magnetocrystalline anisotropy, K₁ contribution from the octahedral and tetrahedral Fe⁺³.

One can also see, as found in Bi-free garnet, that the introduction of increasing amounts of Zr⁺⁴ progressively lowers the anisotropy contribution, and very low linewidths are found at Zr=0.35, albeit with some reduction in Curie temperature. The expected result is a higher Curie temperature from the Bi content being offset by the Zr contribution.

As further shown in FIG. 10, although the 4πM_(s) value generally increases with Zr content, the effect on the K₁/M_(s) contribution is overwhelmingly on K₁, representing a significant technical breakthrough.

FIG. 11 shows various properties as functions of Bi content for the second configuration (Bi_(x)Y_(2.65−x)Ca_(0.35)Zr_(0.35)Fe_(4.65)O₁₂) where Zr⁺⁴ content was fixed at approximately 0.35 while Bi⁺³ content was varied. FIG. 12 shows dielectric constant and density as functions of Bi content for the same configuration. One can see that a large increase in dielectric constant occurs when Bi content is greater than approximately 1. In some implementations, such an increased dielectric constant can be utilized to yield RF devices having desirable features.

It appeared that the maximum Bi⁺³ content was 1.4 in the formula, and therefore can be a optimum or desired amount to replace Y⁺³, at least in the range of Zr⁺⁴ substitution examined. At the example desired Bi content of 1.4, there was a desire to optimize the Zr⁺⁴ content to reduce or minimize the linewidth without substantially reducing the Curie temperature. Also considered was a possibility of implementing a range of V+5 substitutions which can yield a range of magnetizations without much reduction in Curie temperature (e.g., as found in Y-based Zr or In Ca—V garnets).

Based at least in part on the foregoing, the following substitutions were tested to optimize or improve Bi-substituted garnet compositions. For example, by using Ca⁺² to balance V⁺⁵, more Y could be displaced, at a rate of 2 Ca⁺² for 1 V⁺⁵. In another example, Zr⁺⁴ can yield 1:1 substitution of Ca⁺² for Y; thus, if Nb⁺⁵ could be used instead on the octahedral site, more Y could be removed from the compositions.

FIG. 13 shows plots of various properties as functions of Zr content that extends beyond the 0.35 limit described in reference to FIG. 10. Such measurements were based on the foregoing selection of Bi content (approximately 1.4) to refine or optimize the Zr content. Based on such measurements, an example Zr content of 0.55 was selected to test effects of variation of V⁺⁵ content.

FIG. 14 shows plots of various properties as functions of V⁺⁵ content. For such measurements, Bi content was held as approximately 1.4, and Zr content was held at approximately 0.55. It is noted that at the maximum V⁺⁵ substitution, the example composition (Bi_(1.4)Ca_(1.6)Zr_(0.55)V_(0.525)Fe_(3.925)O₁₂) is substantially free of rare earth.

In the context of RF applications, following observations can be made for the foregoing example rare earth-free composition (Bi_(1.4)Ca_(1.6)Zr_(0.55)V_(0.525)Fe_(3.925)O₁₂). Dielectric constant is approximately 27; and this is thought to be due to the “lone pair” of electrons on Bi⁺³ which can greatly increase the polarizability of the ion. Dielectric loss is less than 0.0004, which is useful for most applications. Magnetic loss (as linewidth) is approximately 11 Oersted, which is comparable with the best Y based garnets. 4πM_(s) is approximately 1150 Gauss, which is useful for many RF devices such as those used in cellular infrastructures. Curie temperature is approximately 160° C., which is useful for most applications.

Examples of Devices Having Rare Earth Free or Reduced Garnets:

The modified synthetic garnet compositions made in accordance with the preferred embodiments in this disclosure can be utilized as a ferrite material in a number of different devices utilized in magnetic microwave applications, such as ferrite based isolators, circulators and resonators. Isolators and circulators are necessary in all cellular base stations to direct the RF energy and prevent the energy from flowing back and destroying circuit components. Resonators can be used to filter out signals in cellular base stations. The modified synthetic garnet materials disclosed herein are designed to lower the magnetic resonance linewidth and raise the dielectric constant of the ferrite in circulators and isolators, thus allowing for desirable miniaturization of circulator components.

As described herein, garnets having reduced or no rare earth content can be formed, and such garnets can have desirable properties for use in devices for applications such as RF applications. In some implementations, such devices can be configured to take advantage of unique properties of the Bi⁺³ ion.

For example, the “lone pair” of electrons on the Bi⁺³ ion can raise the ionic polarizability and hence the dielectric constant. This is consistent with the measurement observed in reference to FIG. 14. In that example, the dielectric constant roughly doubled, from 15 to 27 as one went from standard YCaZrV garnets to BiCaZrV garnets when Bi was at maximum substitution at 1.4 in the formula. Such an increase in dielectric constant can be utilized in a number of ways.

For example, because the center frequency of a ferrite device (such as a garnet disk) operating in a split polarization transverse magnetic (TM) mode is proportional to 1/(ε)^(1/2) doubling the dielectric constant (ε) can reduce the frequency by a factor of square root of 2 (approximately 1.414). As described herein in greater detail, increasing the dielectric constant by, for example, a factor of 2, can result in a reduction in a lateral dimension (e.g., diameter) of a ferrite disk by factor of square root of 2. Accordingly, the ferrite disk's area can be reduced by a factor of 2. Such a reduction in size can be advantageous since the device's footprint area on an RF circuit board can be reduced (e.g., by a factor of 2 when the dielectric constant is increased by a factor of 2). Although described in the context of the example increase by a factor of 2, similar advantages can be realized in configurations involving factors that are more or less than 2.

Reduced Size Circulators/Isolators Having Ferrite with High Dielectric Constant:

As described herein, ferrite devices having garnets with reduced or no rare earth content can be configured to include a high dielectric constant property. Various design considerations concerning dielectric constants as applied to RF applications are now described. In some implementations, such designs utilizing garnets with high dielectric constants may or may not necessarily involve rare earth free configurations.

Values of dielectric constant for microwave ferrite garnets and spinels commonly fall in a range of 12 to 18 for dense polycrystalline ceramic materials. Such garnets are typically used for above ferromagnetic resonance applications in, for example, UHF and low microwave region, because of their low resonance linewidth. Such spinels are typically used at, for example, medium to high microwave frequencies, for below resonance applications, because of their higher magnetization. Most, if not substantially all, circulators or isolators that use such ferrite devices are designed with triplate/stripline or waveguide structures.

Dielectric constant values for low linewidth garnets is typically in a range of 14 to 16. These materials can be based on Yttrium iron garnet (YIG) with a value of approximately 16, or substituted versions of that chemistry with Aluminum or, for example, Zirconium/Vanadium combinations which can reduce the value to around 14. Although for example Lithium Titanium based spinel ferrites exist with dielectric constants up to close to 20, these generally do not have narrow linewidths; and thus are not suitable for many RF applications.

As described herein, garnets made using Bismuth substituted for Yttrium can have much higher dielectric constants. Also as described herein, when Zirconium is used in tandem with Bismuth substitution to maintain low linewidths, then the dielectric constant of the garnet can increase as shown by way of examples in Table 2.

TABLE 2 Dielectric 4πM_(s) Linewidth Density Composition Constant (Gauss) (Oersted) (g/cc) Bi_(0.5)Ca_(0.35)Y_(2.15)Zr_(0.35)Fe_(4.65)O₁₂ 18.93 1985 25 5.485 Bi_(0.9)Ca_(0.35)Y_(1.75)Zr_(0.35)Fe_(4.65)O₁₂ 21.35 1925 67 5.806 Bi_(1.4)Ca_(0.35)Y_(1.25)Zr_(0.35)Fe_(4.65)O₁₂ 31.15 1857 52 6.041

Table 2 shows that it is possible to more than double the dielectric constant of garnets. In some implementations, an increase in dielectric constant can be maintained for compositions containing Bismuth, including those with other non-magnetic substitution on either or both of the octahedral and tetrahedral sites (e.g., Zirconium or Vanadium, respectively). By using ions of higher polarization, it is possible to further increase the dielectric constant. For example, Niobium or Titanium can be substituted into the octahedral or tetrahedral site; and Titanium can potentially enter both sites.

In some implementations, a relationship between ferrite device size, dielectric constant, and operating frequency can be represented as follows. There are different equations that can characterize different transmission line representations. For example, in above-resonance stripline configurations, the radius R of a ferrite disk can be characterized as

R=1.84/[2π (effective permeability)×(dielectric constant)]^(1/2)   (1)

where (effective permeability)=H_(dc)+4πM_(s)/H_(dc), with H_(dc) being the magnetic field bias. Equation 1 shows that, for a fixed frequency and magnetic bias, the radius R is inversely proportional to the square root of the dielectric constant.

In another example, in below-resonance stripline configurations, a relationship for ferrite disk radius R similar to Equation 1 can be utilized for weakly coupled quarter wave circulators where the low bias field corresponds to below-resonance operation. For below-resonance waveguide configurations (e.g., in disk or rod waveguides), both lateral dimension (e.g., radius R) and thickness d of the ferrite can influence the frequency. However, the radius R can still be expressed as

R=λ/[2π(dielectric constant)^(1/2)][((πR)/(2d))²+(1.84)²]^(1/2),   (2)

which is similar to Equation 1 in terms of relationship between R and dielectric constant.

The example relationship of Equation 2 is in the context of a circular disk shaped ferrites. For a triangular shaped resonator, the same waveguide expression can used, but in this case, A (altitude of the triangle) being equal to 3.63×λ/2π applies instead of the radius in the circular disk case.

In all of the foregoing example cases, one can see that by increasing the dielectric constant (e.g., by a factor of 2), one can expect to reduce the size of the ferrite (e.g., circular disk or triangle) by a factor of square root of 2, and thereby reduce the area of the ferrite by a factor of 2. As described in reference to Equation 2, thickness of the ferrite can also be reduced.

In implementations where ferrite devices are used as RF devices, sizes of such RF devices can also be reduced. For example, in a stripline device, a footprint area of the device can be dominated by the area of the ferrite being used. Thus, one can expect that a corresponding reduction in device size would be achieved. In a waveguide device, a diameter of the ferrite being used can be a limiting factor in determining size. However, a reduction provided for the ferrite diameter may be offset by the need to retain waveguide-related dimensions in the metal part of the junction.

Examples of Reduced-Size Ferrite Having Yttrium Free Garnet:

As described herein, ferrite size can be reduced significantly by increasing the dielectric constant associated with garnet structures. Also as described herein, garnets with reduced Yttrium and/or reduced non-Y rare earth content can be formed by appropriate Bismuth substitutions. In some embodiments, such garnets can include Yttrium-free or rare earth free garnets. An example RF device having ferrite devices with increased dielectric constant and Yttrium-free garnets is described in reference to FIGS. 15-17.

FIGS. 15A and 15B summarize the example ferrite size reductions described herein. As described herein and shown in FIG. 15A, a ferrite device 200 can be a circular-shaped disk having a reduced diameter of 2R′ and a thickness of d′. The thickness may or may not be reduced. As described in reference to Equation 1, the radius R of a circular-shaped ferrite disk can be inversely proportional to the square root of the ferrite's dielectric constant. Thus, the increased dielectric constant of the ferrite device 200 is shown to yield its reduced diameter 2R′.

As described herein and shown in FIG. 15B, a ferrite device 200 can also be a triangular-shaped disk having a reduced side dimension of S′ and a thickness of d′. The thickness may or may not be reduced. As described in reference to Equation 2, the altitude A of a triangular-shaped ferrite disk (which can be derived from the side dimension S) can be inversely proportional to the square root of the ferrite's dielectric constant. Thus, the increased dielectric constant of the ferrite device 200 is shown to yield its reduced dimension S′.

Although described in the context of example circular and triangle shaped ferrites, one or more features of the present disclosure can also be implemented in other shaped ferrites.

To demonstrate the foregoing effect of the dielectric constant on the operating frequency (and size in some implementations), circulator (sometimes also referred to as an isolator) devices were built. One circulator was built with a current ferrite available as TransTech TTVG1200 (17.56 mm diameter, 1 mm thickness). Another circulator was built with a Yttrium free ferrite with the same dimensions. For the purpose of description, such a Yttrium free ferrite is referred to as “TTHiE1200.” Each of the two example circulators has a diameter of about 25 mm.

The TTVG1200 ferrite has a Yttrium Calcium Zirconium Vanadium Iron garnet configuration, and a typical dielectric constant of approximately 14.4. The Yttrium free ferrite (TTHiE1200) has a Bismuth Calcium Zirconium Vanadium Iron garnet configuration containing not more than approximately 1% rare earth oxides, and a dielectric constant of approximately 26.73.

Additional details concerning the foregoing example circulators are described in reference to FIGS. 16A and 16B, in which a “ferrite” can be the first type (TTVG1200) or the second type (TTHiE1200).

FIGS. 16A and 16B show an example of a circulator 300 having a pair of ferrite disks 302, 312 disposed between a pair of cylindrical magnets 306, 316. Each of the ferrite disks 302, 312 can be a ferrite disk having one or more features described herein. FIG. 16A shows an un-assembled view of a portion of the example circulator 300. FIG. 16B shows a side view of the example circulator 300.

In the example shown, the first ferrite disk 302 is shown to be mounted to an underside of a first ground plane 304. An upper side of the first ground plane 304 is shown to define a recess dimensioned to receive and hold the first magnet 306. Similarly, the second ferrite disk 312 is shown to be mounted to an upper side of a second ground plane 314; and an underside of the second ground plane 314 is shown to define a recess dimensioned to receive and hold the second magnet 316.

The magnets 306, 316 arranged in the foregoing manner can yield generally axial field lines through the ferrite disks 302, 312. The ferrite disks can have a magnetic resonance linewidth of 11 Oe or less. The magnetic field flux that passes through the ferrite disks 302, 312 can complete its circuit through return paths provided by 320, 318, 308 and 310 so as to strengthen the field applied to the ferrite disks 302, 312. In some embodiments, the return path portions 320 and 310 can be disks having a diameter larger than that of the magnets 316, 306; and the return path portions 318 and 308 can be hollow cylinders having an inner diameter that generally matches the diameter of the return path disks 320, 310. The foregoing parts of the return path can be formed as a single piece or be an assembly of a plurality of pieces.

The example circulator device 300 can further include an inner flux conductor (also referred to herein as a center conductor) 322 disposed between the two ferrite disks 302, 312. Such an inner conductor can be configured to function as a resonator and matching networks to the ports (not shown).

FIG. 17 shows insertion loss plots and return loss plots for the two above-described 25 mm circulators (based on the TTVG1200 ferrite (YCaZrVFe garnet, dielectric constant of 14.4), and based on the Yttrium free ferrite (TTHiE1200) (BiCaZrVFe garnet, dielectric constant of 26.73)). Frequencies and loss values for edges of the loss curves of the two circulators (“TTVG1200” and “TTHiE1200”) are indicated by their respective trace markers shown in FIG. 17 and listed in Table 3.

TABLE 3 Marker Trace Frequency Loss value 1 Insertion loss (Y-free TTHiE1200) 1.77 GHz  −0.40 dB 2 Insertion loss (Y-free TTHiE1200) 2.23 GHz  −0.39 dB 3 Insertion loss (TTVG1200) 2.41 GHz  −0.39 dB 4 Insertion loss (TTVG1200) 3.01 GHz  −0.41 dB 5 Return loss (Y-free TTHiE1200) 1.77 GHz −19.87 dB 6 Return loss (Y-free TTHiE1200) 2.23 GHz −16.64 dB 7 Return loss (TTVG1200) 2.41 GHz −16.37 dB 8 Return loss (TTVG1200) 3.01 GHz −18.75 dB

Based on the foregoing measurements, one can see that the TTVG1200 configuration has a center operating frequency of about 2.7 GHz, and the TTHiE1200 configuration has a center operating frequency of about 2.0 GHz. The ratio of center operating frequencies between TTHiE1200 and TTVG1200 configurations is approximately 0.74. It is noted that a theoretical reduction in frequency due to a higher dielectric constant can be calculated (e.g., using Bosma's equations) as being proportional to square root of the ratios of the dielectric constants. Thus, such a calculation yields sqrt(14.4/26.73)=0.734, which is in good agreement with the measured reduction of 0.74.

For the example 25 mm circulators having the TTHiE1200 and TTVG1200 configurations, a comparison of intermodulation yields the following measurements. For 2×40 W tones at room temperature, the TTVG1200 configuration yields an intermodulation performance of approximately −78 dBc at 2.7 GHz, and the TTHiE1200 configuration yields an intermodulation performance of approximately −70 dBc at 1.8 GHz. It is noted that such results are expected due to the reduction in the biasing magnetic field.

To further characterize the TTHiE1200 ferrite as described herein, a smaller 10 mm circulator was made using a TTHiE1200 ferrite disk (radius of approximately 7.00 mm, thickness of approximately 0.76 mm). FIGS. 18A and 18B show s-parameter data for the 10 mm device at operating temperatures of 25 oC and 100 oC, respectively. Intermodulation measurements were also made for the 10 mm device at 25 oC. For 2×15 W tones, intermodulation values are listed in Table 4, where various parameters are indicated in the “Parameter” column.

TABLE 4 Intermodulation Parameter (dBc) 2 × 15 W @ 2110 & 2115 MHz, −59.9 3^(rd) Order IMD @ 2105 MHz 2 × 15 W @ 2110 & 2115 MHz, −58.8 3^(rd) Order IMD @ 2120 MHz 2 × 15 W @ 2138 & 2143 MHz, −57.5 3^(rd) Order IMD @ 2133 MHz 2 × 15 W @ 2138 & 2143 MHz, −56.7 3^(rd) Order IMD @ 2148 MHz 2 × 15 W @ 2165 & 2170 MHz, −56.0 3^(rd) Order IMD @ 2160 MHz 2 × 15 W @ 2165 & 2170 MHz, −54.9 3^(rd) Order IMD @ 2175 MHz

Based on FIGS. 18A and 18B, one can see that the s-parameter data appears to be generally positive. Based on Table 4, IMD performance is generally what is expected for this size package. For example, typical IMD performance for a 20 mm device is about −70 dBc, and about −60 dBc for a 15 mm device.

Various examples of new garnet systems and devices related thereto are described herein. In some embodiments, such garnet systems can contain high levels of Bismuth, which can allow formation of low loss ferrite devices. Further, by selected addition of other elements, one can reduce or eliminate rare earth content of garnets, including commercial garnets. Reduction or elimination of such rare earth content can include, but is not limited to, Yttrium. In some embodiments, the garnet systems described herein can be configured to significantly increase (e.g., double) the dielectric constant of non-Bi garnets, thereby offering the possibility of significantly decreasing (e.g., halving) the printed circuit “footprint” of ferrite devices associated with conventional garnets.

In some implementations as described herein, a synthetic garnet material can include a structure having dodecahedral sites, with Bismuth occupying at least some of the dodecahedral sites. In some embodiments, such a garnet material can have a dielectric constant value of at least 18.0, 19.0, 20.0, 21.0, 22.0, 23.0, 24.0, 25.0, 26.0, or 27.0.

In some embodiments, ferrite-based circulator devices having one or more features as described herein can be implemented as a packaged modular device. FIG. 19 shows an example packaged device 400 having a circulator device 300 mounted on a packaging platform 404 and enclosed by a housing structure 402. The example platform 404 is depicted as including a plurality of holes 408 dimensioned to allow mounting of the packaged device 400. The example packaged device 400 is shown further include example terminals 406 a-406 c configured to facilitate electrical connections.

In some embodiments, a packaged circulator/isolator such as the example of FIG. 19 can be implemented in a circuit board or module. Such a circuit board can include a plurality of circuits configured to perform one or more radio-frequency (RF) related operations. The circuit board can also include a number of connection features configured to allow transfer of RF signals and power between the circuit board and components external to the circuit board.

In some embodiments, the foregoing example circuit board can include RF circuits associated with a front-end module of an RF apparatus. As shown in FIG. 20, such an RF apparatus can include an antenna 412 that is configured to facilitate transmission and/or reception of RF signals. Such signals can be generated by and/or processed by a transceiver 414. For transmission, the transceiver 414 can generate a transmit signal that is amplified by a power amplifier (PA) and filtered (Tx Filter) for transmission by the antenna 412. For reception, a signal received from the antenna 412 can be filtered (Rx Filter) and amplified by a low-noise amplifier (LNA) before being passed on to the transceiver 414. In the example context of such Tx and Rx paths, circulators and/or isolators 400 having one or more features as described herein can be implemented at or in connection with, for example, the PA circuit and the LNA circuit.

In some embodiments, circuits and devices having one or more features as described herein can be implemented in RF applications such as a wireless telecommunication base-station. Such a wireless base-station can include one or more antennas 412, such as the example described in reference to FIG. 20, configured to facilitate transmission and/or reception of RF signals. Such antenna(s) can be coupled to circuits and devices having one or more circulators/isolators as described herein. In some embodiments, the base can have a transceiver, a synthesizer, an RX filter, a TX filter, magnetic isolators and an antenna. The magnetic isolators can be incorporated in a single channel PA and connectorized, integrated triplate or microstrip drop-in. In some implementations, the magnetic isolators comprise a modified synthetic garnet material having at least some of the Yttrium substituted in accordance with certain embodiments described in this disclosure and having magnetic properties equivalent to conventional synthetic garnets.

As described herein, terms “circulator” and “isolator” can be used interchangeably or separately, depending on applications as generally understood. For example, circulators can be passive devices utilized in RF applications to selectively route RF signals between an antenna, a transmitter, and a receiver. If a signal is being routed between the transmitter and the antenna, the receiver preferably should be isolated. Accordingly, such a circulator is sometimes also referred to as an isolator; and such an isolating performance can represent the performance of the circulator.

One-Piece Tunable Ferrite Rod using Modified Synthetic Garnet Compositions

In some embodiments, a one-piece tunable ferrite rod can be formed from the above described synthetic garnet, though other materials can be used as well and the particular material is not limiting. This one-piece tunable ferrite rod can be incorporated into or used with many types of radiofrequency devices, such as resonators. FIG. 21 illustrates a general embodiment of such a resonator with a cavity having a ferrite rod located inside. In some embodiments, the ferrite rod can be a one-piece ferrite rod as discussed below. FIG. 21 illustrates both a top view and a side view of a resonator cavity with a ferrite rod, as well as the respective magnetic and electrical field directions.

Resonators can be used in filters for different types of radiofrequency operations, such as telecommunication base stations having cellular towers/systems. However, filters, and thus the resonators, used in cellular towers/systems often need to be reconfigured to different frequencies during operation in order to properly function. This reconfiguration can be done either off-site, such as by removal and mechanical re-tuning of resonators used within the filter, or on-site, such as by electric motor-driven tuners activated remotely. However, there are numerous drawbacks to these types of tuning. For off-site tuning, tuning can be a substantially slow process, as the resonator needs to be removed and replaced. For on-site motor driving tuning, while faster than off-site tuning, the tuning can still only be done the range of milli-seconds. Therefore, increased tuning speeds can be advantageous in the use of resonators in filters.

FIG. 22 illustrates a dielectric rod used in the prior art. As shown, the complete rod 150 contains multiple pieces, specifically a ceramic puck and a separate ceramic tuning element. The tuning element must be placed within the ceramic puck in order to tune the resonator, typically through a motor driven tuning. Accordingly, the two-piece resonator of the prior art requires the use of a high dielectric constant material as a puck, and a separate magnetic ferrite material as the tuning element. The overall cost of this two-piece structure can be high, as two different material pieces are needed. Further, the hole for the tuning element must be properly formed, thus increasing manufacturing costs. Moreover, as mentioned above, this type of resonator can only be tuned at a speed of around seconds. The tuning can be limited by the stepper motor speed used to move the tuning element.

FIG. 23 illustrates an embodiment of a single-piece tunable ferrite rod which can be manufactured from synthetic garnets, such as those described above, as well as other materials. This single-piece tunable ferrite can be advantageous over two-piece structures of the prior art (such as those shown in FIG. 22) due to the ease of manufacturing as well as its increased tuning speeds. As shown, the ferrite rod 202 can be formed from one solid piece of material. No secondary tuning element is required, as the rod 202 can be directly tuned by a magnetic field. Thus, the rod 202 can be tuned without the requirement of a separate tuning element as in the prior art. This one-piece structure can be achieved by using the synthetic garnet materials described above, which have a high dielectric constant allowing both dielectric resonator properties, as well as magnetic tunability. Therefore, the one-piece ferrite rod is a significant improvement over the two-piece resonators of the art. Further, advantageously embodiments of the one-piece ferrite rod can be tuned in the realm of micro or milliseconds, which can be significantly faster than two-piece resonators of the prior art. In some embodiments, the rod can be tuned by a current changing rapidly in an electromagnetic coil, though other methods of tuning can be used as well and the type of tuning is not limiting.

In some embodiments, ferrite material shaped into a rod can be useful in TM mode, as the rod has a favorable demagnetization factor, reducing the strength of any magnetic bias for setting and tuning the resonant frequency. A resonator can have a height d2 of approximately 0.10, 0.20, 0.30, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.90, 0.95, or 1.00″, and a diameter d1 of approximately 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, or 1.00″. The size and shape of the resonator is not limiting, and other sizes and shapes of resonators can be used. For example, the one-piece resonator can be rectangular in shape.

FIG. 24A illustrates a side viewpoint of an embodiment of a resonator having a cavity 210. As shown, the one-piece ferrite rod 202 can be located generally central within the inner wall 216, having dimensions d3 and d4, of cavity 212 so that there is a gap 214 surrounding the rod 202. In some embodiments, the rod 202 may not be centered in the cavity 212. In some embodiments, there may be no gap 214, and the rod 202 can be flush against the inner wall 216 of the cavity 212. For example d3 could equal d1 and d2 could equal d4.

In some embodiments, a magnetic field 220 can pass through the cavity 210, and thus the one-piece tunable rod 202, where the magnetic field 220 is orthogonal to the top plane of the rod 202. However, the direction of the field 220 is not limiting, and other field directions can be used as well. The cavity 212 can be, for example, silver plated, although the material characteristics of the cavity are not limiting. In some embodiments, silver coatings can help to maximize the Q in the resonator.

FIG. 24B illustrates a top down viewpoint of an embodiment of the resonator cavity configuration shown in FIG. 24A. As shown in the figure, the one-piece ferrite rod 202 can be generally circular, although the shape of the ferrite rod is not limiting. The magnetic field 220 can pass through the top of the resonator 202 so that it is orthogonal to the top plane of the rod 202. In some embodiments, the rod 202 can fit directly within the cavity 212 with no space between the one-piece ferrite rod 202 and the inner wall 216 of the cavity 212. Further, in some embodiments the cavity 212 can have connector-hole ports 222 and 224 cut out of the cavity 212. The connector-hole ports 222 and 224 can be used for coupling RF energy into the cavity 212.

FIG. 25 illustrates an embodiment of a constructed resonator system. The one-piece rod 202 can be located centrally within cavity 212. In some embodiments, the height of the resonator 202 can be approximately the same as that of the cavity 212. In some embodiments, the height of the resonator 202 can be exactly the same height as that of the cavity 212. The one-piece rod 202 can be supported by upper and lower floors 232 a/b of cavity 212.

FIG. 26 illustrates data from DC field tuning of an embodiment of a single-piece ferrite rod of TTHiE 12000, using a silver plated TM mode cavity, 1.024″ diameter x 0.45″ height, with a full height ferrite rod (0.45″) and 0.44″ diameter. TTHiE has a 4PiMs of 1150 Gauss and a dielectric constant of 26.7. The dielectric loss of TTHiE 12000 at 9 GHz was 0.0005, giving a QF product of 18000 GHz. Only the above resonance high Qu region is shown, with cavity/ferrite Q>2000 from 1920 to >2054 MHz, an average QF product of 4000 Ghz in this cavity size. The same cavity containing a standard dielectric with a material QF of 40000 gives a cavity/dielectric QF product of approximately 6000 GHz. An electromagnet was used to tune the DC field.

FIG. 27 illustrates another embodiment of a constructed resonator system. The one-piece rod 202 can be located on a support inside the cavity 212. Accordingly, the rod 202 can be substantially smaller than the cavity 212 in some embodiments. Again, the one-piece rod 202 can be supported by upper and lower floors 232 a/b of cavity 212.

For a TE mode experiment, shown in FIG. 28, a TTHiE 12000 disk 0.44″ diameter×0.176″ thick was used, mounted in the geometric center of a 1.5″ diameter×0.6″ height silver plated cavity, using Styrofoam to locate the disk. Because of the gap above and below the disk, and the disk demagnetization factor, only below resonance measurements were made, due to field limitations of the DC electromagnet. However, the high frequencies avoid any low field loss contribution to magnetic losses. The onset of ferromagnetic resonance can be seen at the highest DC field used. The highest Qu measured was approximately 2000, a QF of 12000 GHz. The same cavity with a standard dielectric with a material QF product of 40000 would give a QF product for the cavity/dielectric of at least 30,000 GHz, indicating the TE mode is less useful below ferromagnetic resonance compared with the TM mode above ferromagnetic resonance.

FIG. 29 illustrates a method of forming a tunable resonator 300. In step 302, a ferrite rod without a tuning element can be formed 302, such as through embodiments described below. The ferrite rod can be formed from a synthetic garnet such as those described above. The ferrite rod can be assembled within a resonance cavity 304. In step 306, the system can be capable of providing an adjustable magnetic field to the ferrite rod and resonance cavity. This magnetic field can allow for tuning of a resonant frequency without the introduction of a tuning element to the ferrite rode.

FIG. 30 illustrates a method for tuning an embodiment of a resonator using a ferrite rod not having a separate tuning rode 310. In step 312, it can be determined whether a change in resonant frequency of the resonator is desired. If a change in resonant frequency is desired 314, a change in the resonator can be introduced such that a static magnetic field provided to a high-dielectric rod changes to yield a desired resonant frequency without utilizing a separate tuning element 316.

In some embodiments, the above described resonator can be used in a cavity filter element as a TM or TE mode resonator, such as one shown in FIG. 31. The ferrite rod can be biased either in a range of DC magnetic fields below resonance, or a range above resonance. When used in either situation, the tenability can derive from the tunable permeability of the ferrite with changing DC bias field. In some embodiments, the frequency of the operation can exceed 4 PiMs×gamma×appropriate demagnetization factor (in MHz), thereby avoiding low field losses. In some embodiments, the DC magnetic bias can be electromagnetic, a DC magnetic field, or a combination of both for setting and tuning the resonator.

In some embodiments, as shown in FIG. 31, a modified garnet and single-piece ferrite rod, such as those described above, can be used in a filtration system 500. In some embodiments, the system can be composed of numerous elements, such as a baseband sub-system 502, and up converter 504, a Tx filter 506, a PA 508, a filter diplexer 510, and an antenna 514. The system 500 can also be composed of an LNA 516, an Rx filter 518, a mixer 520, an L.O. filter 522, and a local oscillator 524. Embodiments of the modified garnet can be used in the system 500 such as, for example, in the filters.

The tenability of the above describe material can be due to the variation of the permeability of the synthetic garnet within a magnetic field, both above and below ferromagnetic resonance. Within the ferromagnetic resonance, tenability may be affected by high absorption losses. The resonance of the resonator is a separate physical effect from the ferromagnetic resonance of the ferrite bar, e.g. the garnet.

In some embodiments, the resonator can have temperature stability of frequency after tuning through the use of magnetic alloys with certain selected, near room temperature, Curie temperatures.

In some embodiments, the above described single-piece tunable ferrite rod can greatly reduce cost and manufacturing time of both the tunable rod as well as the complete multi-element filter, which has one combined element per pole instead of two, as shown in FIG. 31. Base station filters can have approximately 3 poles, and multiplexed versions can have 20 or more. Therefore, the single-piece tunable ferrite rod can greatly reduce the manufacturing time for the larger multiplexed filters.

FIGS. 32-36 illustrate processes for fabricating ferrite devices having one or more features as described herein. FIG. 32 shows a process 20 that can be implemented to fabricate a ceramic material having one or more of the foregoing properties. In block 21, powder can be prepared. In block 22, a shaped object can be formed from the prepared powder. In block 23, the formed object can be sintered. In block 24, the sintered object can be finished to yield a finished ceramic object having one or more desirable properties.

In implementations where the finished ceramic object is part of a device, the device can be assembled in block 25. In implementations where the device or the finished ceramic object is part of a product, the product can be assembled in block 26.

FIG. 32 further shows that some or all of the steps of the example process 20 can be based on a design, specification, etc. Similarly, some or all of the steps can include or be subjected to testing, quality control, etc.

In some implementations, the powder preparation step (block 21) of FIG. 32 can be performed by the example process described in reference to FIG. 8. Powder prepared in such a manner can include one or more properties as described herein, and/or facilitate formation of ceramic objects having one or more properties as described herein.

In some implementations, powder prepared as described herein can be formed into different shapes by different forming techniques. By way of examples, FIG. 33 shows a process 50 that can be implemented to press-form a shaped object from a powder material prepared as described herein. In block 52, a shaped die can be filled with a desired amount of the powder. In FIG. 34, configuration 60 shows the shaped die as 61 that defines a volume 62 dimensioned to receive the powder 63 and allow such power to be pressed. In block 53, the powder in the die can be compressed to form a shaped object. Configuration 64 shows the powder in an intermediate compacted form 67 as a piston 65 is pressed (arrow 66) into the volume 62 defined by the die 61. In block 54, pressure can be removed from the die. In block 55, the piston (65) can be removed from the die (61) so as to open the volume (62). Configuration 68 shows the opened volume (62) of the die (61) thereby allowing the formed object 69 to be removed from the die. In block 56, the formed object (69) can be removed from the die (61). In block 57, the formed object can be stored for further processing.

In some implementations, formed objects fabricated as described herein can be sintered to yield desirable physical properties as ceramic devices. FIG. 35 shows a process 70 that can be implemented to sinter such formed objects. In block 71, formed objects can be provided. In block 72, the formed objects can be introduced into a kiln. In FIG. 36, a plurality of formed objects 69 are shown to be loaded into a sintering tray 80. The example tray 80 is shown to define a recess 83 dimensioned to hold the formed objects 69 on a surface 82 so that the upper edge of the tray is higher than the upper portions of the formed objects 69. Such a configuration allows the loaded trays to be stacked during the sintering process. The example tray 80 is further shown to define cutouts 83 at the side walls to allow improved circulation of hot gas at within the recess 83, even when the trays are stacked together. FIG. 36 further shows a stack 84 of a plurality of loaded trays 80. A top cover 85 can be provided so that the objects loaded in the top tray generally experience similar sintering condition as those in lower trays.

In block 73, heat can be applied to the formed objects so as to yield sintered objects. Such application of heat can be achieved by use of a kiln. In block 74, the sintered objects can be removed from the kiln. In FIG. 36, the stack 84 having a plurality of loaded trays is depicted as being introduced into a kiln 87 (stage 86 a). Such a stack can be moved through the kiln (stages 86 b, 86 c) based on a desired time and temperature profile. In stage 86 d, the stack 84 is depicted as being removed from the kiln so as to be cooled.

In block 75, the sintered objects can be cooled. Such cooling can be based on a desired time and temperature profile. In block 206, the cooled objects can undergo one or more finishing operations. In block 207, one or more tests can be performed.

Heat treatment of various forms of powder and various forms of shaped objects are described herein as calcining, firing, annealing, and/or sintering. It will be understood that such terms may be used interchangeably in some appropriate situations, in context-specific manners, or some combination thereof.

From the foregoing description, it will be appreciated that an inventive resonator is disclosed. While several components, techniques and aspects have been described with a certain degree of particularity, it is manifest that many changes can be made in the specific designs, constructions and methodology herein above described without departing from the spirit and scope of this disclosure.

Certain features that are described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can, in some cases, be excised from the combination, and the combination may be claimed as any subcombination or variation of any subcombination.

Moreover, while methods may be depicted in the drawings or described in the specification in a particular order, such methods need not be performed in the particular order shown or in sequential order, and that all methods need not be performed, to achieve desirable results. Other methods that are not depicted or described can be incorporated in the example methods and processes. For example, one or more additional methods can be performed before, after, simultaneously, or between any of the described methods. Further, the methods may be rearranged or reordered in other implementations. Also, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems can generally be integrated together in a single product or packaged into multiple products. Additionally, other implementations are within the scope of this disclosure.

Conditional language, such as “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include or do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments.

Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require the presence of at least one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than or equal to 10% of, within less than or equal to 5% of, within less than or equal to 1% of, within less than or equal to 0.1% of, and within less than or equal to 0.01% of the stated amount.

Some embodiments have been described in connection with the accompanying drawings. The figures are drawn to scale, but such scale should not be limiting, since dimensions and proportions other than what are shown are contemplated and are within the scope of the disclosed inventions. Distances, angles, etc. are merely illustrative and do not necessarily bear an exact relationship to actual dimensions and layout of the devices illustrated. Components can be added, removed, and/or rearranged. Further, the disclosure herein of any particular feature, aspect, method, property, characteristic, quality, attribute, element, or the like in connection with various embodiments can be used in all other embodiments set forth herein. Additionally, it will be recognized that any methods described herein may be practiced using any device suitable for performing the recited steps.

While a number of embodiments and variations thereof have been described in detail, other modifications and methods of using the same will be apparent to those of skill in the art. Accordingly, it should be understood that various applications, modifications, materials, and substitutions can be made of equivalents without departing from the unique and inventive disclosure herein or the scope of the claims. 

What is claimed is:
 1. A tunable resonator system comprising: a cavity; a single-piece high-dielectric resonator comprising a tunable magnetic element formed out of one material and located within the cavity; and an adjustable magnetic field.
 2. The tunable resonator system of claim 1 wherein the resonator has millisecond tuning.
 3. The tunable resonator system of claim 1 wherein the resonator has micro-second tuning.
 4. The tunable resonator system of claim 1 wherein the cavity has a silver coating.
 5. The tunable resonator system of claim 1 wherein the single-piece high-dielectric resonator has a dielectric constant of 26.7.
 6. The tunable resonator system of claim 1 wherein the resonator is a TE mode resonator.
 7. The tunable resonator system of claim 1 wherein the resonator is a TM mode resonator.
 8. The tunable resonator system of claim 1 wherein the material is a synthetic garnet.
 9. The tunable resonator system of claim 8 wherein the synthetic garnet is Bi_(x)Ca_(y+2x)Y_(3−x−y−2z)Fe_(5−y−z)Zr_(y)V_(z)O₁₂.
 10. The tunable resonator system of claim 8 wherein the synthetic garnet is Bi_(x)Y_(3−x−0.35)Ca_(0.35)Zr_(0.35)Fe_(4.65)O₁₂.
 11. The tunable resonator system of claim 8 wherein the synthetic garnet is Bi(Y,Ca)₂Fe_(4.2)M^(I) _(0.4)M^(II) _(0.4)O₁₂.
 12. The tunable resonator system of claim 8 wherein the synthetic garnet is Y_(2.15−2x)Bi_(0.5)Ca_(0.35+2x)Zr_(0.35)V_(x)Fe_(4.65−x)O₁₂.
 13. The tunable resonator system of claim 8 wherein the synthetic garnet is Bi_(0.9)Ca_(0.9x)Y_(2.1−0.9x)(Zr_(0.7)Nb_(0.1))_(x)Fe_(5−0.8x)O₁₂.
 14. The tunable resonator system of claim 8 wherein the synthetic garnet is Bi_(0.9)Ca_(0.9+2x)Y_(2.1−0.9−2x)Zr_(0.7)Nb_(0.1)V_(x)Fe_(4.2−x)O₁₂.
 15. The tunable resonator system of claim 8 wherein the synthetic garnet is Bi_(1.4)Ca_(0.55+2x)Y_(1.05−2x)Zr_(0.55)V_(x)Fe_(4.45−x)O₁₂.
 16. The tunable resonator system of claim 8 wherein the synthetic garnet is Y₂CaFe_(4.4)Zr_(0.4)Mo_(0.2)O₁₂.
 17. The tunable resonator system of claim 8 wherein the synthetic garnet is a material selected from the group consisting of BiY₂Fe_(4.6)In_(0.4)O₁₂, BiCa_(0.4)Y_(1.6)Fe_(4.6)Zr_(0.4)O₁₂, BiCa_(0.4)Y_(1.6)Fe_(4.6)Ti_(0.4)O₁₂, BiCa_(0.8)Y_(1.2)Fe_(4.6)Sb_(0.4)O₁₂, BiY₂Fe_(4.6)Ga_(0.4)O₁₂, BiCa_(1.2)Y_(0.8)Fe_(4.2)In_(0.4)Mo_(0.4)O₁₂, BiY_(1.2)Ca_(0.8)Fe_(4.2)Zn_(0.4)Mo_(0.4)O₁₂, BiY_(1.2)Ca_(0.8)Fe_(4.2)Mg_(0.4)Mo_(0.4)O₁₂, BiY_(0.4)Ca_(1.6)Fe_(4.2)Zr_(0.4)Mo_(0.4)O₁₂, BiY_(0.4)Ca_(1.6)Fe_(4.2)Sn_(0.4)Mo_(0.4)O₁₂, BiCa₂Fe_(4.2)Ta_(0.4)Mo_(0.4)O₁₂, BiCa₂Fe_(4.2)Nb_(0.4)Mo_(0.4)O₁₂, BiY_(0.8)Ca_(1.2)Fe_(4.6)Mo_(0.4)O₁₂, and BiY_(0.4)Ca_(1.6)Fe_(4.2)Ti_(0.4)Mo_(0.4)O₁₂.
 18. A filtration system comprising: an antenna; a subsystem; a converter; and at least one filter having a single-piece high-dielectric resonator comprising a tunable magnetic element formed out of one material.
 19. A method of forming a tunable resonator system comprising: preparing a powder for a high-dielectric material; forming the powder into a shape; and sintering the formed powder into a single-piece high-dielectric resonator comprising a tunable magnetic element formed out of one material and located within the cavity.
 20. The method of claim 19 further comprising inserting the single-piece high-dielectric resonator into a cavity and applying an adjustable magnetic field. 